1. Field Of The Invention
This invention relates to novel polyols, to polymer/ polyols utilizing such polyols and to polyurethanes prepared from such polymer/polyols.
2. Description Of The Prior Art
Polymer/polyol compositions suitable for use in producing polyurethane foams, elastomers and the like are known materials. Such compositions can be produced by polymerizing one or more ethylenically unsaturated monomers dissolved or dispersed in a polyol in the presence of a free radical catalyst. These polymer/polyol compositions have the valuable property of imparting to, for example, polyurethane foams and elastomers produced therefrom, higher load-bearing properties than are provided by the corresponding unmodified polyols.
There are a number of prior disclosures relating to production of polymer/polyol compositions. The basic patents in the field are Stamberger U.S. Pat. Re. No. 28,715 (reissue of U.S. Pat. No. 3,383,351) and U.S. Pat. Re. No. 29,118 (reissue of U.S. Pat. No. 3,304,273). Other prior disclosures include: British Pat. No. 1,126,025; Scharf et al. Canadian Pat. No. 735,010; Kuryla Canadian Pat. No. 785,835; Pizzini et al. U.S. Pat. No. 3,652,639; Pizzini et al. U.S. Pat. Re. No. 29,014 (reissue of U.S. Pat. No. 3,823,201); Patton, Jr., et al. U.S. Pat. No. 3,950,317; Ramlow et al. U.S. Pat. No. 3,953,393; DeWald U.S. Pat. No. 3,655,553; Fabris et al. U.S. Pat. No. 3,850,861; Priest et al. U.S. Pat. No. 4,208,314; Simroth U.S. Pat. No. 4,104,236; Shah U.S. Pat. No. 4,148,840; Shah U.S. Pat. No. 4,119,586; Shook et al. U.S. Pat. No. 4,172,825; Drake et al. U.S. Pat. No. 4,198,488; Preston et al. U.S. Pat. No. 4,198,488; Japanese Pat. No. 48-101494; Japanese Pat. No. 52-80919/75;and Van Cleve et al. U.S. Pat. No. 4,357,430.
The polymer/polyol compositions that found initial commercial acceptance were primarily compositions produced using acrylonitrile. Such compositions were somewhat higher in viscosity than desired in some applications. Further, such compositions were at least primarily used commercially in producing foams under conditions such that the heat generated during foaming is readily dissipated (e.g.--the foams have a relatively thin cross-section) or under conditions such that relatively little heat is generated during foaming. When polyurethane foams were produced under conditions such that the heat generated during foaming was not readily dissipated, severe foam scorching usually resulted. Later, polymer/polyol compositions produced from acrylonitrile-methylmethacrylate monomer mixtures were commercialized and were convertible to polyurethane foams having reduced scorch.
More recently, polymer/polyol compositions produced from acrylonitrile-styrene monomer mixtures have been used commercially. Use of low ratios of acrylonitrile-to-styrene in the monomer mixture affords polymer/polyols that do not give rise to a scorch problem. But it is increasingly difficult to make satisfactorily stable polymer/polyols as the ratio of acrylonitrile to styrene is reduced to the desired levels, particularly at high polymer contents.
The development of sophisticated, high speed and large volume equipment, machines and systems for handling, mixing and reacting polyurethane-forming ingredients has created the need for highly stable polymer/polyols. At one time, there was not much concern for the seediness, viscosity or filterability of polymer/polyols in actual commercial practice. However, the state of the art of polyurethane production has now advanced to the point where these considerations are very important in many applications. There is now much concern with filterability, seediness, and viscosity; and polymer/polyols must meet certain minimum requirements in order to be capable of being processed in the sophisticated foam equipment now used. Typically, the prime requirement is that the polymer/polyols possess sufficiently small particles so that filters, pumps and the like do not become plugged or fouled in relatively short periods of time.
While somewhat simplified, the commercial processability of a particular polymer/polyol comes down to its viscosity and stability against phase separation. Lower viscosities are of substantial practical and economic significance due to the ease of pumping and metering as well as ease of mixing during the formation of polyurethanes. Stability is a prime consideration in insuring that the polymer/polyols can be processed in commercial production equipment without the necessity of additional mixing to insure uniformity.
In addition to the monomer ratio in acrylonitrile-styrene polymer/polyols, other recognized factors that affect product stability include polyol molecular weight and polymer content.
In producing polymer/polyols for use in certain polyurethane elastomer applications, relatively low molecular weight polyols are typically utilized to provide the requisite product stiffness. However, it has been found that it is increasingly difficult to make satisfactorily stable polymer/polyols as the molecular weight of the polyol is decreased.
Still other applications could desirably utilize polyurethane foams and elastomers with even higher load-bearing characteristics than can be currently provided using available polymer/polyols. However, it has been found that it is increasingly difficult to make satisfactory dispersion stable polymer/polyols as the amount of polymer is increased.
U.S. Pat. No. 4,208,314 to Priest et al. discloses low viscosity polymer/polyols made from acrylonitrile-styrene monomer mixtures. These polymer/polyols can be converted to low density, water blown polyurethane foams having reduced scorch, especially when the acrylonitrile to styrene ratio is relatively low. The Priest et al. patent also provides a process for making polymer/polyols whereby the particulate nature of the product is considerably improved, compared to polymer/polyols prepared by prior processes. Using prior procedures, such as the one disclosed in Canadian Pat. No. 735,010, polymer/polyols formed from such monomer mixtures usually contained excessive amounts of large granules. The improved process provided by Priest et al. includes, in general, maintaining a low monomer concentration throughout the reaction mixture during the polymerization.
U.S. Pat. No. 4,104,236 to Simroth discloses a substantial further improvement in forming polymer/polyols made from acrylonitrile/styrene monomer mixtures, which enables selection of the polymer content to provide a polymer/polyol having satisfactory stability when a polyol of given molecular weight and a monomer mixture having a ratio of acrylonitrile to styrene within a certain range are used. The Simroth patent also highlights the fact that satisfactory product stability is not obtained when many combinations of otherwise desirable composition parameters are used.
U.S. Pat. No. 4,172,825 to Shook et al. discloses further improvements in the formation of polymer/polyols. As discussed therein, polymer/polyol compositions exhibiting outstanding properties can be made by utilizing a specific type of peroxide catalyst, namely t-alkyl peroxyester catalysts. By utilizing this specific type of catalyst, polymer/polyols can be produced on a commercial basis which have outstanding properties, such as filterability in processing, yet which allow either the polymer or the styrene content to be increased. Also, polymer/polyols can be produced on a commercial scale with polyols having a molecular weight lower than had been used prior to this invention.
A further improvement in the formation of polymer/polyols is provided by U.S. Pat. No. 4,148,840 to Shah, which discloses a process for producing highly stable and filterable polymer/polyol compositions by polymerizing the monomer or monomers in situ in a polyol mixture that includes a minor amount of preformed polymer/polyol.
Yet another improvement is disclosed in U.S. Pat. No. 4,119,586 to Shah, which discloses a process for producing highly stable polymer/polyol compositions by polymerizing the monomer or monomers in situ in a polyol mixture that includes a major amount of a low molecular weight polyol and a minor amount of high molecular weight polyol.
U.S. Pat. No. 4,242,249 to VanCleve et al. discloses yet another approach to producing stable polymer/polyols in cases where the composition parameters are such that conventional processes would not usually afford a stable product. In the process disclosed by this patent, the monomer mixture is polymerized in a polyol that contains a minor amount of a preformed stabilizer that is tailored to the monomer mixture used. The stabilizer is a copolymer comprised of an anchor portion that is a polymer of the monomer mixture, and a solvatable portion consisting of a propylene oxide polymer having a number average molecular weight of at least about 800.
It has been recognized that the stability of polymer/polyols requires the presence of a minor amount of a graft or addition copolymer which is formed in situ from the monomer and polyol. Some prior approaches have thus been directed to the deliberate incorporation of amounts of unsaturation to the polyol in addition to that inherently present in the polyoxyalkylene polyols typically used in forming polymer/polyols in the belief that improved stability will result due to an increased amount of an addition copolymer stabilizer expected to be formed. U.S. Pat. Nos. 3,652,639, 3,823,201, and 3,850,861, British Pat. No. 1,126,025, and Japanese Pat. Nos. 52-80919 and 48-101494 all utilize this approach.
U.S. Pat. No. 3,850,861 thus discloses the in situ polymerization of ethylenically unsaturated monomers in an unsaturated polyol. Suitable polyols are prepared by using an ethylenically unsaturated polyhydric initiator to form a polyalkylene oxide. The examples set forth include dibasic acids or their derivatives, such as maleic acid. The polyol polymerization medium contains one mole of unsaturation per mole of polyol.
U.S. Pat. No. 3,652,639 likewise discloses the in situ polymerization of ethylenically unsaturated monomers in an ethylenically unsaturated polyol medium. The unsaturated polyols of this patent are produced in a manner similar to those of U.S. Pat. No. 3,823,201, as will be discussed hereinafter, except that the level of unsaturation is higher, being on the order of 1 to 3 moles of unsaturation per mole of polyol.
U.S. Pat. No. 3,823,201 discloses a method of preparing a polymer/polyol by the in situ polymerization of ethylenically unsaturated monomers in a polyol having from 0.1 to 0.7 mole of unsaturation per mole of polyol. Unsaturation at the levels set forth in the U.S. Pat. No. 3,652,639 patent were indicated as imparting unnecessarily high viscosities to the resulting polymer/polyols. The unsaturation level that is added can be introduced into the polyol by, for example, reacting it with an ethylenically unsaturated compound that is capable of adding to the polyol by reaction with the hydroxyl group, such as maleic anhydride. The polymer/polyols disclosed in U.S. Pat. No. 3,823,201 are asserted to be highly stable due to the presence of the stabilizing species which is formed via the grafting (i.e.--by copolymerization) of vinyl polymer chain segments to the unsaturated polyol molecules. Certain improvements in polyurethanes using such polymer/polyols are likewise asserted. More particularly, it is stated that such polymer/polyols are surprisingly superior to those prepared from polyols having high unsaturation in regard to their low viscosities. It is further stated that polyurethane foams prepared from these graft copolymers exhibit superior load-bearing properties.
British Pat. No. 1,126,025 discloses in situ polymerization of ethylenically unsaturated monomers in a polyol having a molecular weight from 250 to 10,000, preferably from 300 to 7,000, and containing at least 0.7 double bonds per molecule. It is stated that suitable unsaturated polyols can be made by including unsaturated compounds such as unsaturated polyhydric alcohols, polycarboxylic acids, or epoxides in the reaction mixture when the polyol is formed, but that it is preferred to introduce the unsaturation by reacting a preformed polyol with an unsaturated epoxide, e.g., allyl glycidyl ether.
Japanese Pat. No. 52-80919 discloses products that are said to be useful in preparation of polyurethanes which are produced by polymerizing unsaturated polyether-esters, or copolymerizing an unsaturated polyether-ester with a vinyl monomer. The unsaturated polyether-ester is prepared by reacting a polyol having a molecular weight of 1,000, to 30,000 with a mixture of saturated and unsaturated dicarboxylic acids. It is stated that the mole ratio of saturated dicarboxylic acid to unsaturated dicarboxylic acid should be from 95/5 to 50/50 to control polymerization. In the Examples, the products are described as being homogeneous and stable.
Japanese Pat. No. 48-101494 discloses in situ polymerization of ethylenically unsaturated monomers in modified polyether polyols obtained by reacting a polyether polyol first with an unsaturated dicarboxylic acid anhydride in an amount more than 0.2 mole per mole of polyol, and then with an epoxy compound, preferably an alkylene oxide, in an amount of preferably 1.1 to 1.5 moles per mole of unsaturated dicarboxylic acid anhydride.
A further approach to production of polymer/polyols is disclosed in U.S. Pat. No. 4,198,488 to Drake et al. In the process disclosed in this patent, the monomer mixture that is polymerized in the polyol includes a minor amount of an ethylenically unsaturated dicarboxylic acid anhydride. It was theorized that some graft copolymer is produced in situ when a portion of the dicarboxylic acid anhydride units that have polymerized into the polymer undergo an esterification reaction with the hydroxyl groups of the polyol. And it was further theorized that the graft copolymer formed in this way acts as a stabilizer for the polymer dispersion.
While many of the above techniques relating to polymer/polyol preparation have provided improved and beneficial results, there are certain cases where none of these techniques have provided products which were entirely satisfactory. Thus, for example, in some situations, the use of the blended base polyol approach results in an undue lowering of the hydroxyl number of the blend with a resultant adverse effect upon foam performance. Other approaches, while generally satisfactory, are too expensive for many commercial applications, too complicated, result in color and odor problems or require foam reformulations which can create undue difficulties.
It is highly desirable for low density slab stock foam applications to be able to provide white, virtually scorch-free products. This can be accomplished at foam densities of about 3.0 pounds per cubic foot or so. It may also be possible with existing technology to provide foams with scorch-free characteristics at even lower densities; but, typically, the technology used either requires an economic penalty or results in less than satisfactory foam characteristics. There thus remains the need to provide techniques capable of producing, without substantial economic penalty, white, virtually scorch-free slab stock foams at ever decreasing densities (viz. --1.5 pounds per cubic foot or less) while maintaining satisfactory load-bearing and other foam properties.
Further, some foam applications require quite rigorous combustibility resistance. It is quite difficult with existing technology to provide polymer/polyols that can be employed to prepare foams meeting such requirements. There thus remains an unfilled need to provide technology which can provide satisfactory polymer/polyols, yet satisfy these rigorous combustibility standards.
The copending Meschke et al. application identified herein discloses connected branch copolymers comprising three parts: a basic or starter segment which will be referred to herein for convenience as a "core" segment; branching polymer segments, comprising polymeric entities connected to at least one end of the core segment and which provide sites for further polymerization; and linear polymer segments, which comprise essentially linear polymeric entities connected to the branch polymer at its reactive branching sites. The core segment has a valence of v, wherein v is an integer, and has correspondingly v terminal bonds connected to v polyvalent, non-crosslinked, branching polymer segments. Each branching polymer segment has an average of t terminal bonds, wherein t is greater than about 2, and is connected to a set of linear polymer segments, which have an average of t-1 linear polymer segments per set. There is thereby provided a group of about v (t-1) linear polymer segments wherein the linear polymer segments have substantially similar chain lengths and composition within that group.
Such copolymers provide superior properties such as reduced viscosity at a given molecular weight. More specifically, polyalkylene oxide connected branch copolymers have thus been shown to have lowered viscosities when compared to linear or star polyalkylene oxide polymers of similar molecular weight.
Belgian Pat. No. 845,72 relates to a method of preparing polypropylene glycols with reduced double bond content by the polymerization of propylene oxide in the presence of basic catalyst and optionally of a solvent. It is stated that, by the presence of a relatively small amount of glycidol, one obtains a considerable reduction of the double bond content of the polypropylene glycol, without the terminal hydroxyl group content being modified in a noticeable way.